We obtain room-temperature resistivities as low as ρ =1.4 x 10-4 Ω-cm in transparent Ga-doped ZnO
grown on Al2O3 by pulsed laser deposition (PLD) at 200 °C in 10 mTorr of pure Ar and then
annealed in a Zn enfivironment. Donor ND and acceptor NA concentrations are calculated
from a recently developed scattering theory that is valid for any degenerate semiconductor material
and requires only two input parameters, mobility μ and carrier concentration n measured at any
temperature in the range 5 - 300 K. By comparison with SIMS and positron annihilation
measurements, it has been shown that the donors in these samples are mostly GaZn, as expected, but
that the acceptors are point defects, Zn vacancies VZn. PLD growth in Ar at 200 °C produces a high
concentration of donors [GaZn] = 1.4 x 1021 cm-3, but VZn acceptors are produced at the same time,
due to self-compensation. Fortunately, a large fraction of the VZn can be eliminated by annealing in a Zn environment. The theory gives ND and NA, and thus [GaZn] and [VZn], at each step of
the growth and annealing process. For convenience, the theory is presented graphically, as plots of μ
vs n at various values of compensation ratio K = NA/ND. From the value of K corresponding to the
experimental values of μ and n, it is possible to calculate ND = n/(1 - K) and NA = nK/(1 - K).

Optical methods are powerful and non-destructive means to characterize highly doped transparent conducting oxide thin
films. In order to describe the optical properties of high-mobility ZnO films we present a dielectric function composed of
different analytic expressions to describe the different contributions to the dielectric function of the films. This allows for
the correct description of measured optical spectra and reduces the complex functions to a set of fitting parameters. In a
second step we compare the obtained parameters to theoretical models. The basic theories are nicely reproduced and the
basic link between optical and electrical properties can be understood. The findings can help on the route to a complete
presiction of optical properties from the basic material properties or vice versa.

Bulk ZnO crystals were grown by the hydrothermal technique with Ga2O3 or GaN added to the solution in an
attempt to dope with Ga, or co-dope with Ga and N, respectively. Adding Ga2O3 alone to the growth solution
significantly reduces the ZnO growth rate; however, the resulting crystal is highly conductive, with a resistivity
approaching 0.01 Ω cm. In contrast, the addition of GaN had less effect on the growth of ZnO, but the crystal was of
poor quality with a higher resistivity, about 0.1 Ω cm. Photoluminescence spectra at 4 K show Ga0-bound-exciton peak
energies of 3.3604 and 3.3609 eV for the Ga- and Ga/N-doped crystals, respectively; these energies differ slightly from
the literature value of 3.3598 eV, evidently due to compressive strain. Other peaks at 3.307, 3.290, 3.236, and 3.20 eV
were found in the Ga/N-codoped ZnO after the crystal was annealed at 600°C in air. The 3.307 eV peak is the so-called
A line, and likely arises from recombination of a free electron with a neutral N-related acceptor.

High quality ZnO films have been obtained by utilizing buffer layers fabricated via nitrogen mediated crystallization
(NMC), where sputtering method is employed for preparation of both buffer layers and ZnO films. The crystal grain size
of ZnO:Al (AZO) films with NMC-buffer layers is about 3 times larger than that of conventional films, which is
considered to be due to the low nuclei density of NMC-buffer layers. As a result, the resistivity of AZO films drastically
reduces from 4.76 m Ωcm for the conventional films to 0.48 m Ωcm for our films when the total film thickness is 20
nm. The NMC buffer layers also improve the spatial distribution of the resistivity, which indicates that the crystallinity at
the initial stage of deposition govern the properties of AZO films. Furthermore, we have succeeded in epitaxial growth of
ZnO films, whose FWHM of the rocking curve of (002) peak is as narrow as 0.061°, on c-plane sapphire substrates by
using the NMC method. From these results, we conclude that our method described here is full of promise for fabrication
of ZnO-based materials.

Doped ZnO is one of the materials currently being considered in commercial optoelectronic
applications as a potential indium tin oxide (ITO) replacement for the transparent conducting oxide (TCO).
The properties of doped ZnO anodes prepared at Arkema Inc. are analyzed using spectroscopic
ellipsometer (230 to 1700 nm) and Hall-effect. The modeling of the refractive indexes is conducted using a
double oscillator model. The model parameters are tested on a double layer: undoped and doped structure
deposited by atmospheric pressure chemical vapor deposition (APCVD) on glass substrates. Excellent
correlation between calculated and experimental parameters was obtained.

The continuously increasing power of modern supercomputers renders the application of more and more accurate parameterfree
models to systems of increasing complexity feasible. Consequently, it becomes possible to even treat different realstructure
effects such as alloying or n-doping in systems like the technologically important transparent conducting oxides.
In this paper we outline how we previously used a combination of quasiparticle calculations and a cluster expansion scheme
to calculate the fundamental band gap of MgxZn1-xO and CdxZn1-xO alloys. We discuss the results in comparison to
values for In2O3, SnO2, SnO, and SiO2. In addition, we discuss our extension of the Bethe-Salpeter approach that has
been used to study the interplay of excitonic effects and doping in n-type ZnO. The dependence of the Burstein-Moss shift
on the free-carrier concentration is analyzed.

Arsenic-doped ZnO films were fabricated by radio frequency magnetron sputtering method with different substrate
temperature TS. Growing with the low substrate temperature of TS=200°C yielded n-type semi-insulating sample.
Increasing the substrate temperature would yield p-type ZnO film and reproducible p-type film could be produced at
TS~450°C. Post-growth annealing of the n-type As-doped ZnO sample grown at the low substrate temperature
(TS=200°C) in air at 500°C also converted the film to p-type conductivity. Further increasing the post-growth annealing
temperature would convert the p-type sample back to n-type. With the results obtained from the studies of positron
annihilation spectroscopy (PAS), photoluminescence (PL), cathodoluminescence (CL), X-ray photoelectron
spectroscopy (XPS), secondary ion mass spectroscopy (SIMS) and nuclear reaction analysis (NRA), we have proposed
mechanisms to explain for the thermal process induced conduction type conversion as observed in the As-doped ZnO
films.

Monoclinic gallium oxide, β-Ga2O3, is a transparent conducting oxide (TCO) that presents one of the widest band gaps
among this family of materials. Its characteristics make it highly interesting for applications in UV - visible - IR
optoelectronic and photonic devices. On the other hand, the morphology of nanowires made of this oxide presents
specific advantages for light emitting nanodevices, waveguides and gas sensors. Control of doping of the nanostructures
is of the utmost importance in order to tailor the behavior of these devices.
In this work, the growth of the nanowires is based on the vapor-solid (VS) mechanism during thermal annealing
treatment while the doping process was carried out in three different ways. In one of the cases, doping was obtained
during the growth of the wires. A second method was based on thermal diffusion of the dopants after the growth of
undoped nanowires, while the third method used ion implantation to introduce optically active ions into previously
grown nanowires. The study of the influence of the different dopants on the luminescence properties of gallium oxide
nanowires is presented. In particular, transition metals and rare earths such as Cr, Gd, Er or Eu were used as optically
active dopants that allowed selection of the luminescence wavelength, spanning from the UV to the IR ranges. The
benefits and drawbacks of the three different doping methods are analyzed. The waveguiding behavior of the doped
nanowires has been studied by room temperature micro-photoluminescence.

Large-diameter, lithium-free ZnO single-crystal substrates of high crystalline quality will enable development and
commercialization of high-performance ZnO-based semiconductor devices, such as UV and visible light emitting diodes
(LEDs), UV laser diodes and solar-blind UV detectors for variety of applications. We have recently developed a novel
crystal growth technique for producing lithium-free ZnO single crystal boules of 1 inch in diameter. We also fabricated
ZnO single crystal wafers in sizes up to 1 inch in diameter. Chemical purity, crystalline defects, and electrical resistivity
of ZnO single crystals were analyzed. Results from crystal growth and material characterization are presented and
discussed. Our research results suggest that the novel crystal growth technique is a viable production technique for
producing ZnO single crystals and substrates for semiconductor device applications.

We succeeded in fabricating ZnO microspheres with high sphericity by laser ablation in superfluid helium. Such
microspheres enable efficient lasing in the whole visible region due to defects with a CW laser at room temperature. The
lasing threshold is found to be around 100 W/cm2. This value is much smaller than those of the recent reports on the
lasing in ZnO microwire. Cathodoluminescence of single ZnO microspheres was also measured.

The use of silicon superlattices is a well established technique for creating nanocrystals. Depositing superlattices allows
for adjustment of nanocrystal properties, such as the emission wavelength, by varying the silicon layer thickness.
Opposed to the silicon layer, the silicon dioxide thickness effects are not documented as extensively. This study looks at
superlattice films with silicon and silicon dioxide layers varying from 0.4 to 0.8 nm and 2.7 to 5.1 nm respectively,
deposited via a plasma enhanced chemical vapor deposition. Photoluminescence and electroluminescence measurements
were taken to show an increase in the output intensity increased oxide thickness.

We report on white light emission from zinc oxide nanostructures chemically grown on paper substrates. The
effect of the growth solution pH on the morphology is discussed. The light emission form light emitting diodes
based on ZnO nanorods/organic polymer hybrids on paper substrate is presented. Further copper oxide was
grown on the walls of zinc oxide nanorods and the optical properties were investigated.

Nanowires (NWs)-based light emitting diodes (LEDs) have drawn large interest due to many advantages compared to
thin film based devices. Markedly improved performances are expected from nanostructured active layers for light
emission. Nanowires can act as direct waveguides and favor light extraction without the use of lenses and reflectors.
Moreover, the use of wires avoids the presence of grain boundaries and then the emission efficiency should be boosted
by the absence of non-radiative recombinations at the joint defects. Electrochemical deposition technique was used for
the preparation of ZnO-NWs based light emitters. Nanowires of high structural and optical quality have been epitaxially
grown on p-GaN single crystalline films substrates. We have shown that the emission is directional with a wavelength
that was tuned and red-shifted toward the visible region by doping with Cu in ZnO NWs.

Optical properties of In2O3 nanoparticles coated with polyvinyl-alcohol (PVA) are studied. Compared with uncoated
In2O3 nanoparticles, PVA coated sample show enhanced UV-blue emission and suppressed parasitic green emission.
Ultraviolet (UV)-blue photodetectors were then fabricated by depositing aluminum (Al) as contacts on top of PVA
coated and uncoated samples. The photodetector with PVA coating, exhibits lower dark current and higher responsivity
than the photodetector without PVA coating. The rise and fall time of the PVA coated photodetector is about 500 s and
1600 s respectively, one half of the uncoated device. These improvements are attributed to surface passivation of In2O3
nanoparticles by PVA, which reduces the surface defects density and increase free carrier concentration of In2O3
nanoparticles.

We demonstrated growth of YAG, LuAG and CALGO single crystal fibers with doping Nd, Yb, Er, and Ce by the
micro-pulling-down technique. Those fibers have applications in high power lasers and scintillating detectors. For laser
operation, average power of 65 W energy of 4 mJ and peak power above 7 MW have been demonstrated in various
configurations. Those results push the limits of end-pumped bulk crystals in terms of average power and exceed the
limits of pulsed fibers lasers in terms of energy. For scintillating applications, high density/high light yield detectors are
developed for nuclear science and medical applications.

GaN was grown on ZnO-buffered c-sapphire (c-Al2O3) substrates by Metal Organic Vapor Phase
Epitaxy. The ZnO then served as a sacrificial release layer, allowing chemical lift-off of the
GaN from the c-Al2O3 substrate via selective wet etching of the ZnO. The GaN was subsequently
direct-wafer-bonded onto a glass substrate. X-Ray Diffraction, Scanning Electron Microscopy,
Energy Dispersive X-ray microanalysis, Room Temperature Photoluminescence & optical
microscopy confirmed bonding of several mm2 of crack-free wurtzite GaN films onto a soda
lime glass microscope slide with no obvious deterioration of the GaN morphology. Using such
an approach, InGaN based devices can be lifted-off expensive single crystal substrates and
bonded onto supports with a better cost-performance profile. Moreover, the approach offers the
possibility of reclaiming and reusing the substrate.

In this paper we show the application of Rutherford backscattering spectrometry and ion channeling
(RBS/C) for the detection of compositional and strain gradients in CdZnO grown almost
pseudomorphically on MgZnO. The asymmetric features revealed in X-ray diffraction studies were
explained by the compositional gradient found in the first 100 nm close to the interface. Calculations of
the effect of such a gradient on the strain state of the layer were developed and contrasted with RBS/C
angular scans. Additionally, the substitutional behavior of Cd (and Mg) in Zn-sites was demonstrated.

Photoluminescence (PL) studies of the surface exciton peak in ZnO nanostructures at ~3.367 eV are
reported to elucidate the nature and origin of the emission and its relationship to nanostructure
morphology. Localised voltage application in high vacuum and different gas atmospheres show a
consistent PL variation (and recovery), allowing an association of the PL to a bound excitonic
transition at the ZnO surface modified by an adsorbate. Studies of samples treated by plasma and of
samples exposed to UV light under high vacuum conditions show no consistent effects on the
surface exciton peak indicating no involvement of oxygen species. X-ray photoelectron spectroscopy
data indicate involvement of adsorbed OH species. The relationship of the surface exciton peak to
the nanostructure morphology is discussed in light of x-ray diffraction, scanning and transmission
electron microscopy data.

The temperature dependence of diffusion length and lifetime or diffusivity of the free exciton is measured in a
commercial ZnO-substrate and in an epitaxial ZnO quantum well using nm-spatially and ps-time resolved
cathodoluminescence (CL) spectroscopy. The characteristic temperature dependence of the exciton mobility is a
fingerprint of the underlying excitonic scattering processes. Since excitons are neutral particles scattering at ionized
impurities should be not effective. With decreasing temperature diffusion lengths and lifetimes give rise to a monotonous
increase of the excitonic mobility. Two different methods for determining the excitonic transport parameters will be
presented. On the one hand we are able to perform completely pulsed excitation experiments and on the other hand a
combination of cw- and pulsed excitation in two independent measurements are needed.

BaTiO3 (BTO) single crystals exhibit one of the largest Pockels coefficients (r42 > 1000 pm/V) among oxides. This makes
BTO an excellent active material for electro-optical (EO) devices such as switches, modulators or tuning elements.
However, in order to harness these properties in silicon photonics circuits, the challenge is to integrate BTO as high
quality thin films onto Si substrates. The effective Pockels coefficients can be enhanced in epitaxial films due to their
tight relationship with the crystallographic symmetry and microstructure.
We report on the EO properties of epitaxial BTO thin films on Si. The growth of BTO layers on Si(001) is performed by
molecular beam epitaxy (MBE). A thin single-crystalline strontium titanate seed layer is grown on Si, followed by a
130 nm thick BTO layer. Electrodes to provide an electrical field parallel to the surface are patterned on the films using
photolithography. Throughout this process, the BTO keeps an epitaxial relationship to the Si-substrate.
Considering the tensor nature of the Pockels effect, the optical behavior of the BTO layers upon applying an electrical
field is simulated, taking into account the films' crystalline multi-domain structure. An experimental way to access these
EO properties is discussed, which utilizes polarization changes of a transmitted laser beam upon applying an electrical
field to the film. Simulations of the measurement signals demonstrate the capability of resolving the expected EO
response of the samples, which serves as a promising base for future experiments.

Optical absorption bands in two complex oxides are characterised using ab initio simulations and an embedded
cluster method. In sub-nanoporous 12CaO.7Al2O3 the width of the optical gap can be controlled by modifying
the chemical identities and relative concentration of extra-framework species. In antiferromagnetic LaCrO3, Cr
3d states split into four narrow one-electron bands and give rise to several types of the optical transitions. Their
excitation energies respond differently to lattice strain, thus, providing a possibility for tuning the excitation
energies in supported LaCrO3 films by selecting appropriate substrates.

The understanding of the interaction of organic species with inorganic surfaces and nanostructures constitutes a step
forward in the development of novel hybrid devices, such as sensors and solar cells. In this work the structural and
electronic properties of clean and defective ZnO non-polar surfaces modified with acetic acid have been investigated by
using the self-consistent charge density-functional based tight-binding method (SCC-DFTB). In particular, the
adsorption of acetic acid, the role of surface defects and the relevant mechanisms acting on surface stabilization are
discussed.

In this paper we perform a systematic investigation and optimization of lambda controlled, reactive ion beam sputter
deposition process conditions for a range of optical materials. The deposited films are compared for suitability for
applications such as planar waveguides for optical interconnect, laser device manufacture, multi-layer interference filters,
and precision optical mirrors. Thin films of tantalum pentoxide and aluminum oxide were deposited using a reactive
dual-magnetron sputtering system (Leybold Optics Helios Pro). Deposited film quality was optimized as a function of
plasma power and gas flow, and an optimum oxygen working point was determined for each material. Lambda control
methods were used for the purpose of optimizing optical quality of the layer. Deposited layers were characterized by
variable angle spectroscopic ellipsometry (VASE), X-ray diffraction (XRD) and SEM imaging. Waveguide losses were
measured for each sample using a prism coupling arrangement. Tantalum pentoxide slab waveguides with loss as low as
1dB/cm were produced ideal for waveguide applications. Interference filters/mirrors consisting of alternating SiO2, and
Ta2O5 or Al2O3 material layers were deposited and characterized. Reflectivity and transmission of the deposited mirrors
was compared to the theoretical design. Good agreement between the theory and the practical filter/mirror designs was
achieved confirming the material film quality.

P-type thin-film transistors (TFTs) using room temperature sputtered tin and copper oxide as a transparent oxide
semiconductor have been produced on rigid and paper substrates. The SnOx films shows p-type conduction presenting a
polycrystalline structure composed with a mixture of tetragonal β-Sn and α-SnOx phases, after annealing at 200 °C.
These films exhibit a hole carrier concentration in the range of ≈ 1016-1018 cm-3, electrical resistivity between 101-102
Ωcm, Hall mobility of 4.8 cm2/Vs, optical band gap of 2.8 eV and average transmittance ≈ 85 % (400 to 2000 nm).
Concerning copper oxide CuxO thin films they exhibit a polycrystalline structure with a strongest orientation along (111)
plane. The CuxO films produced between an oxygen partial pressure of 9 to 75% showed p-type behavior, as it was
measured by Hall effect and Seebeck measurements. The bottom gate p-type SnOx TFTs present field-effect mobility
above 1.24 cm2/Vs (including the paper p-type oxide TFT) and an on/off modulation ratio of 103 while the CuxO TFTs
exhibit a field-effect mobility of 1.3×10-3 cm2/Vs and an on/off ratio of 2×102.

In this work we present sputtered multicomponent dielectrics based on mixtures of HfO2 and SiO2. This way it is
possible to get stable amorphous structure up to 800ºC, that does not happen for pure HfO2, for instance, that present a
polycrystalline structure when deposited without any intentional substrate heating. Besides, also the band gap of the
resulting films is increased when compared with pure HfO2 that theoretically is an advantage in getting a suitable band
offset with the semiconductor layer on oxide TFTs. Concerning the electrical characterization, the leakage current on c-Si
MIS structures is low as 10-9 Acm-2 at 10 V. The amorphous structure of the films also lead to better
dielectric/semiconductor interfaces, as suggested by C-V characteristics on GIZO MIS structures, which do not present
strong variation with frequency. On other hand, the dielectric constant decreases due to the incorporation of SiO2 and
Al2O3. Further improvement on insulating and interface characteristics is achieved using multilayer stacks and substrate
bias during deposition.

The β-Ga2O3 films were grown on (0001) sapphire at 500 °C by metal organic chemical vapor deposition. In the
analysis of crystal structure, we found that the (-201) oriented single crystal β-Ga2O3 epilayer can be obtained under low
chamber pressure of 15 torr. Moreover, a metal-semiconductor-metal solar-blind deep ultraviolet photodetector was
fabricated with the β-Ga2O3 epilayer. As the bias voltage is 5 V, the photodetector exhibits a relatively low dark current
about 0.2 pA, which induced by the highly resistive nature of the β-Ga2O3 thin films. From the responsivity result, it can
be observed that photodetector shows a maximum responsivity at 260 nm, revealing the β-Ga2O3 photodetector was
really solar-blind. The responsivity of the photodetector was as high as 20.1 A/W with an applied bias of 5 V and an
incident light wavelength of 260 nm. The improved performance is attributed to the high quality of β-Ga2O3 epilayer.

Regarding its ability to circumvent the autofluorescence signal, persistent luminescence was recently shown to be a
powerful tool for in vivo imaging and diagnosis applications in living animal. The concept was introduced with
lanthanide-doped persistent luminescence nanoparticles (PLNP), from a lanthanide-doped silicate host
Ca0.2Zn0.9Mg0.9Si2O6:Eu2+, Mn2+, Dy3+ emitting in the near-infrared window. In order to improve the behaviour of these
probes in vivo and favour diagnosis applications, we showed that biodistribution could be controlled by varying the
hydrodynamic diameter, but also the surface charges and functional groups. Stealth PLNP, with neutral surface charge
obtained by polyethylene glycol (PEG) coating, can circulate for longer time inside the mice body before being uptaken
by the reticulo-endothelial system. However, the main drawback of this first generation of PLNP was the inability to
witness long-term monitoring, mainly due to the decay kinetic after several decades of minutes, unveiling the need to
work on new materials with improved optical characteristics. We investigated a modified silicate host, diopside
CaMgSi2O6, and increased its persistent luminescence properties by studying various Ln3+ dopants (for instance Ce, Pr,
Nd, Tm, Ho). Such dopants create electron traps that control the long lasting phosphorescence (LLP). We showed that
Pr3+ was the most suitable Ln3+ electron trap in diopside lattice, providing optimal trap depth, and resulting in the most
intense luminescence decay curve after UV irradiation. A novel composition CaMgSi2O6:Eu2+,Mn2+,Pr3+ was obtained
for in vivo imaging, displaying a strong near-infrared persistent luminescence centred on 685 nm, allowing improved and
sensitive detection through living tissues.

Magnetic nanoparticles (MNPs), including those of transition metals, such as iron oxide nanoparticles, cobalt oxide
nanoparticles, and ferrite nanoparticles with diameters between 3 nm and 34 nm have been developed by a wet chemical
method. These MNPs were modified with the functional groups, and introduced into cancer cells. SiO2-shelled ferrite
nanoparticles have been discussed for the use in hyperthermia treatments on the basis of measurements of their AC
magnetic susceptibilities.

A dense array of vertical ZnO nanowires on a-plane sapphire substrate was synthesized by a simple chemical vapor
deposition method. The electrolyte-based Schottky contact of the ZnO nanowires was investigated by electrochemical
impedance spectroscopy. An n-type semiconductor behavior and a flat-band potential of about 0 V (0.05 V) versus
Ag/AgCl electrode were obtained for the synthesized ZnO nanowires. The ~ 0 V flat-band potential is suggested to be a
balanced result of (1) the Femi-level difference induced by the Schottky contact at the ZnO/electrolyte interface and (2)
the oxygen vacancy induced surface adsorption effect at the ZnO nanowire surface. Hydrogen plasma treatment was
carried out to passivate the oxygen vacancies in the ZnO nanowires. An obvious shift of the flat-band potential to about -
0.6 V was obtained for the same ZnO nanowire array sample after the hydrogen plasma treatment. The negative flatband
potential, indicating an electron depletion region at the surface of ZnO nanowires, is observed owing to the Fermilevel
difference between the n-type ZnO nanowires and the electrolyte, without a strong influence of the oxygen
vacancy-related surface adsorption effect. Moreover, the carrier density in the ZnO nanowires was increased by almost
four orders of magnitude after the hydrogen plasma treatment. The increase in carrier density confirms existing reports
of hydrogen atoms occupying interstitial sites in the ZnO nanowires in addition to the oxygen vacancies after the
hydrogen plasma treatment.

Molecular beam epitaxy technique has enabled synthesis of atomically smooth thin films, multilayers, and
superlattices of cuprates and other complex oxides. Such heterostructures show high temperature superconductivity and
enable novel experiments that probe the basic physics of this phenomenon. For example, it was established that high
temperature superconductivity and anti-ferromagnetic phases separate on Ångström scale, while the pseudo-gap state
apparently mixes with high temperature superconductivity over an anomalously large length scale (the "Giant Proximity
Effect"). We review some recent experiments on such films and superlattices, including X-ray diffraction, atomic force
microscopy, angle-resolved time of flight ion scattering and recoil spectroscopy, transport measurements, highresolution
transmission electron microscopy, resonant X-ray scattering, low-energy muon spin resonance, and ultrafast
photo-induced reflection high energy electron diffraction. The results include an unambiguous demonstration of strong
coupling of in-plane charge excitations to out-of-plane lattice vibrations, a discovery of interface high temperature
superconductivity that occurs in a single CuO2 plane, evidence for local pairs, and establishing tight limits on the
temperature range of superconducting fluctuations.

The electronic state of T'-type cuprates which exhibit superconductivity without doping was investigated by
polarized x-ray absorption spectroscopy (XAS) for T'-La2CuO4 and T'-(La,Y)2CuO4 thin film single-crystals.
The effect of oxygenation and deoxygenation on the near-edge structures evidences the two processes create
and remove apical oxygen defects that strongly suppress superconductivity. The near-edge spectra further
indicate that the deoxygenation, well known as a common prerequisite for superconductivity, also creates
in-plane oxygen defects, whose contribution to the n-type conduction and superconductivity without doping is
not ruled out. The observed local lattice distortion consistent with the neutron scattering experiment may
influence a long-range magnetic order favoring a metallic state without doping.

Morphology control of semiconductor nanostructures is of great interest in recent years owing to their unique
capabilities in achieving desired chemical and physical properties as well as enabling great potential in electronic and
optoelectronic applications. In this paper, we review our recent study on morphological control of ZnO nanocones and
how the optical and electrical properties of such nanostructure-based photovoltaic solar cells are affected. The nanocone
shape is obtained by altering the ratio of oxygen to argon gas during thermal chemical vapor deposition. The nanocones
grown on Si substrates show antireflective properties in a broad spectral range. We further found that incident light was
confined in the nanocones, which enhances the antireflective properties through multi-reflection/absorption. The
performance dependency of a ZnO-CdTe solar cell on the morphology of ZnO was explored by introducing the
nanocones. Small junction area and strong electric field at the tip of nanocones contribute to effective charge transport
across the heterojunction, resulting in improved the conversion efficiency of solar cells.

Hydrothermal treatment at low temperature (~150 ºC) was performed on different ZnO nanostructures grown on
different substrates such as Si and ITO/glass. The water vapor environment and the high pressure of water vapor at that
temperature were expected to improve the optical properties of ZnO nanorods. Under such mild condition, no significant
morphology changes are expected.
However, significant changes were observed in both morphology and optical properties. The morphology of ZnO
nanostructures has been changed in various ways, depending on the growth conditions of ZnO nanostructures as well as
the substrates. In the terms of optical properties, the increase of photoluminescence (PL) intensity was observed and the
UV to visible ratio of ZnO PL spectra was also improved in some cases, while in others there has been no improvement.
Hydrothermal treatment was also performed on zinc oxide precursor on Si substrates to study the possible Si
contamination during the procedure. Zinc nitrate solution in ethanol was used as the precursor. As a result, an increase of
the intensity of the broad peak around 430 nm which is related to silicon oxide was obtained.

The impact of various masking patterns and template layers on the wet chemically grown vertical ZnO nanowire arrays
was investigated. The nanowires/nanorods were seeded at nucleation windows which were patterned in a mask layer
using various techniques such as electron beam lithography, nanosphere photolithography, and atomic force microscope
type nanolithography. The compared ZnO templates included single crystals, epitaxial layer, and textured polycrystalline
films. Scanning electron microscopy revealed that the alignment and crystal orientation of the nanowires were dictated
by the underlying seed layer, while their geometry can be tuned by the parameters of the certain nanopatterning
technique and of the wet chemical process. The comparison of the alternative nanolithography techniques showed that
using direct writing methods the diameter of the ordered ZnO nanowires can be as low as 30-40 nm at a density of 100-
1000 NW/μm2 in a very limited area (10 μm2-1 mm2). Nanosphere photolithography assisted growth, on the other hand,
favors thicker nanopillars (~400 nm) and enables large-area, low-cost patterning (1-100 cm2). These alternative lowtemperature
fabrication routes can be used for different novel optoelectronic devices, such as nanorod based ultraviolet
photodiode, light emitting device, and waveguide laser.

In luminescence spectra of certain ZnO films there is a second band in the near-ultraviolet region alongside with an
exciton band. With the increasing of pumping this band intensity increases much faster than the intensity of the exciton
band. It is shown that the above second band is not the so called P-line. It is rather connected with shallow level in ZnO
structures. We suggest interpreting the observed effect with a due account of Burstein-Moss effect. For approximate
modeling of the observed process rate equation system has been formulated. It is demonstrated that it is possible to find
such parameters so that the relevant numerical solution gives a dependence of bands emission intensity ratio on pumping
power that simulates quality wise experimental results.

This work reports on investigations into the possibility of harvesting energy from the piezoelectric response
of millimetric ZnO rods to movement. SEM & PL studies of hydrothermally grown ZnO rods revealed
sizes ranging from 1 - 3 mm x 100 - 400 microns and suggested that each was a wurtzite monocrystal.
Studies of current & voltage responses as a function of time during bending with a probe arm gave
responses coherent with those reported elsewhere in the literature for ZnO nanowires or micro-rod single
wire generators. The larger scale of these rods provided some advantages over such nano- and
microstructures in terms of contacting ease, signal level & robustness.

Due to the attractive combination of a relatively high specific heat of combustion with a large
specific energy capacity, molecular hydrogen (H2) is being investigated for use as an alternative to
fossil fuels. Energy-efficient H2 production and safe storage remain key technical obstacles to
implementation of an H2 based economy, however.
ZnO has been investigated for use as an alternative photocatalytic electrode to TiO2 for solarpowered
photo-electro-chemical (PEC) electrolysis, in which H2 is generated by direct water
splitting in a cell with a metal cathode and a semiconducting anode.
In this investigation, ZnO NR grown on Si (100) substrates by pulsed laser deposition were
investigated for use as electrodes in the Hydrogen Evolution Reaction (HER). The electrochemical
potential and Fermi energy of the ZnO NR were estimated from the electrochemical current density
in acid and alkaline solutions via phenomenological thermodynamic analysis. As well as acting as an
effective electrocalytic cathode, the ZnO NR appear to operate as a hydrogen reservoir. These results
indicate that the ZnO NR have excellent potential for the storage of evolved H2.

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Advanced PhotonicsJournal of Applied Remote SensingJournal of Astronomical Telescopes Instruments and SystemsJournal of Biomedical OpticsJournal of Electronic ImagingJournal of Medical ImagingJournal of Micro/Nanolithography, MEMS, and MOEMSJournal of NanophotonicsJournal of Photonics for EnergyNeurophotonicsOptical EngineeringSPIE Reviews